Apparatus for sharpening files



Jan. 9, 1934. A. A. ROTH APPARATUS FOR SHARPENING FILES Filed Aug. 5; 1952 5 Sheets-Sheet 1 A. A. ROTH APPARATUS FOR 'SHARPENING FILES Jan. 9, 1934.

Filed Aug. 5, 1932 5 Sheets-Sheet 2 Jan. 9, 1934. A. A. ROTH 1,942,881

APPARATUS FOR SHARPENING FILES Filed Aug. 5, 1932 5 Sheets-Sheet 3 Jan. 9, 1934. A. A. ROTH 1,942,331

APPARATUS FOR SHARPENING FILES Filed Aug. 5, 1932 5 Sheets-Sheet 4 Jan. 9, 1934. A. A. ROTH 1,942,881

APPARATUS FOR SHARPENING FILES Filed Aug. 5, 1932 5 Sheets-Sheet 5 Patented fan. 9, 1934 UNITED STATES PATENT OFFICE 1,942,881 APPARATUS FOR SHARPENING FILES August A. Both, Baltimore, Md. Application August" 1922. "serial 'Nofezr'tis 8 Claims. (01. 2 c4. 5)

This invention relates to apparatus particularly designed for sharpening files by means of an electrolyte and a current, as described in my co-pending application entitled Apparatus for sharpen-. 5 ing tools, filed October 23, 1931, Serial The principal object of provide apparatus in which Number the invention is to spotting of the elec trolyte due to uneven distribution of current will be positively eliminated so may be used over and over that the electrolyte again, if desired.

Anotherobject of the present invention is to provide an improved heating tankhaving an immersed electric heater therein whereby the Water which forms the heating medium for the electrolyte will be more quickly brought to, and more uniformly maintained at, the desired operating temperature than hitherto possible.

A further object is to provide an iml foved,

mounting in the tank for the earthen vessel which the sharpeningoperation.

A further object is to provide a novelholderror the files which will permit the files bein supported upright and stationary during the sharpening process.

A further object is toprovidea novel cover for the tank adapted to permit escape o f ;vapors and to permit replenishing the tank without disturbing the; water supply in the earthen vessel.

With the above and other objects in view the invention consists in certain novel details of construction and combinati ons of parts hereinafter fully described and claimed it being understood that varlous modifications may be resorted to within the scope of the, appended claims with out departing from the spirit or sacrificing any of the advantages of the inv ention.

In the accompanying drawings forming part of this specification,

Figure l is a vertical section through the apparatus,

Figure 2 is aplan view of the apparatus,

Figure 3 is a plan view'of the tank with the earthen vessel removed and and the immersed electric showing the cathode heaters, c

Figure 4 is a detail horizontal section showing the mounting of the immers Figure 5 is a front elevat and heaters,

ed heaters, ion of the mounting Figure 6 is a plan View of the bottom plate of e hol r.

Figure 7 is a plan view of a modified form of holder, 7 V

Figure fiis a cross section taken on the line -8.o .u

Figure 9 isadetails ction through the. lower part of the apparatusshowing agas heater substituted for the electric heater, .and

. Figure 10 is a diagrammaticview showing the electric, wiring of the apparatus. a I is well known, ordinary methods of sharpening tools, such as dental burrs, files and like multi-edged tools, by an electrolyte and an elect ic current, is unsatisfactorydue to pitting of the. tools, as well as the formation of an objectionable taper that is sharpening of the cutting edges on the side of ,the tool toward the positive electrode, and insufiicient sharpening on the side away from th l c ro e-. 75

Also ,spotting of the electrolyte .occurs, that is, deterioration in spots dueto uneven distribution of current. so that such vspots difier in strength .from, adjoining jportions of the electrolyte and, this spotting not only destroys the electrolyte and rend rs it unfit for further continued usebutalsoaggravates the condition known as pitting and the opposite condition, that is, the formation of deposits on the tools to be sharpened... I i

The pfesenhapbaratus isdesigned to correct these disadvantages by the provision of a novel earthen vessel which containsan electrolyte in which thefilesto besharpened are submerged and. a novel .water; tank inwhich the vessel is .p'laced,.th'e .water in the tank being uniformly heated throughout to'promo-te the flow of current iuniformly in all directions to and from the submergedfiles so that uniform sharpening will be effected throughout the entire superficial area of. the..cutting edges of the files, and spotting positively eliminated.

Ordinarily, .difiiculty has been experienced in bringing the. temperature of the water 'in the tank up tocthe required operating temperature or about 140. F, to 160 Rand maintaining it for the three minute, more or less, timeperiod necessary to efiect thesharpening, so that long, wasteful delays are encounteredas well as changes in temperature throughout. the period. The pres- 0 cut invention obviates this disadvantage. by the provision of arplurality of electric heaters which are submerged infthe water and heat the bath direct without inte'rveningwall's, the heaters being adapted to quickly bring the water up to the 110 operating temperature and maintain it at this temperature during the sharpening operation so that the guess work encountered in apparatus hitherto proposed is entirely eliminated.

Referring now to the drawings in which like characters of reference designate similar parts in the various views, the apparatus is shown to comprise a cylindrical metal tank 10 preferably having double walls 11 between which apacking of heat insulating material 12, such as asbestos is interposed. The walls are preferably formed of metal. Preferably, also the inner wall is provided above its bottom edge with a circumfer-' ential flange 13 upon whichthe bottom edge of the outer wall rests. The outer wall may be reinforced with split reinforcing hoops'14, the ends the other end having a nut 17, which may be tightened against the eye, to draw the hoops snugly in place, as shown in Figure 2. Y

The tank is provided preferably with a sheet metal bottom 18 which is provided witha flange 19 that extends downwardly along the inner wall of the tank and reinforces the same against distortion. The bottom maybe welded, or otherwise rigidly secured to the tank wall.

The tank is provided at the top edge ofthe inner wall with a circumferential flange 20 upon which rests a cover 21, preferably formed of sheet metal. The cover is provided with a central opening 22 of sufficient size to loosely receive the hereinafter described earthen vessel 23 and the cover slopes downwardly from the outer periphery thereof to said opening so-that the contents of the tank may be replenished from time to time by pouring water onto said-cover from whence it passes downwardly through the opening 22 into the tank. The opening '22 also permits escape of vapors from the tank. -The cover is provided with a downwardly extending flange 24 which surrounds the upper portion .of the outer wall of the tank, as shown.

The tank is adapted to'be filled with waterto nearly the top thereof, and for heating the water directly, preferably a pair of immersed electric heaters 25, shown best inv Figure 4, are mounted in an opening 26 formed in the .inner wall of the tank. These heaters extend parallel with the bottom of the tank and are elevated slightly above the bottom and are suflicient in length to extend to substantially the axis of the tank, as shown best in Figure 3.

For mounting the heaters, a substantially oval casting 27, shown best in Figure 5, is provided with a pair of threaded openings 28 .into which the screw threaded insulating bushings 29 of the heaters are received. The casting is provided at the ends with ears 30 which may be welded to the outer surface of the inner wallof the tank. The casting is provided also with a substantially oval flange 31 which projects through the opening 26 and forms a guard flangearound the bases of the heating elements 32 inside the tank; The flange is welded or otherwise rigidly secured .to the edge of the opening 26.to prevent leakage therethrough.

The heaters are of standard type that may be procured on the market and embody asxan essential feature a loop resistance element 33 which is engaged in asheath 34 of high heat conductivity material which prevents water coming in contact with the resistance elements.

As best shown in Figure 4, the outerwall of the tank is bent inwardly around the casting to provide a flange 35 which holds the asbestos packing 12 in place and also defines an opening in the outer wall of the tank to permit easy insertion and removal of the heaters.

Referring again to Figure 1, it will be seen that the earthen vessel is cylindrical in contour. The vessel is preferably an earthen cylindrical jar and may be either glazed or unglazed, but should be of sufficient porosity to permit the electrolyte 36, with which the vessel is filled, to dampen the jar throughout its physical structure and form easy paths for the current from the electrolyte in the jar to the water in the tank andfrom thence through the tank, which forms a part of the cathode, to the low tension terminal of the source of current supply.

of which are tied together by means of an eye 15 on one end and a threaded projection '16 on By referring to Figure 10, it will be seen that one of the heaters may be connected to any suitablesource of alternating current supply by means of circuit wires 37 and 38 controlled by a -switoh'39'to deliverabout 3000 watts, more or less. The other heater is connected by circuit wires-39 and 40 to the source of alternating current, these wires being controlled by a pair of switches 4-1 and-42 which are selectively closed to deliver either 1500 or 3000 watts to the heater. As will be apparent, when the switches 39, 41 and 42 are all closed both heating coils will be energized to maximum capacity for quickly heating the water in the tank. By opening the switch 39 only one of the heaters will be energized and by then opening the switches 41 or 42 said heater will be only partly energized. Thus a predetermined temperature of the fluid in the tank may be maintained after it is quickly brought up to the'operating temperature of from about 140 F.' to 160 F. The heated water bath in the tank produces a corresponding temperature in the electrolyte by conduction through the earthen vessel 23.

As best shown in Figure 1, the files to be sharpened are secured in a holder preferably consisting of an upper disk 43 anda lower disk 44, preferably formed of sheet copper. A spacing block- 45, of insulating material such as bakelite, is interposed between the disks and is provided with an upstanding boss 46 which projects through a central opening in the upper disk. Theboss is interiorly threaded to receive the threaded lower end of a tube 47 which is sufficient in height to extend above the top of the vessel 23. The block is secured to both disks by means of bolts 48. The disks are, furthermore, held in spaced relation by bolts 49 upon which are disposed spacing sleeves 50, these spacing sleeves being disposed between the disks. The bolts, furthermore, are suflicient in length to extend below the bottom disk 44 and have threaded upon them sleeves 51 which form legs to support the disks upon the bottom of the earthen vessel 23. The holder is thus supported stationary on the bottom of the vessel; Both. the insulating block 54 and the lower disk 44 are provided with aligned square central openings, as shown, to reduce weight of these parts. As shown best in Figures 2 and 6, the upper disk is provided with a plurality of oblong openings 55'and the lower disk is provided with a plurality'of small circular openings 56 which alignwith respective ones'o'f'the'oblong openings 55. The -files 57, to be sharpened; 'aremounted on the disks in upright position by passing the shank of each file downwardly through an oblong opening 55 minate short of the boss.

and through a corresponding circular opening 56, as shown in Figure 1. I

The tube 47 of the holder terminates at the top in a ring 58 adapted to receive preferably the bakelite link of a block and tackle, or other hoisting means for lifting the holder with its files out of the electrolyte after the sharpening operation and replacing the holder in the electrolyte filled with the dull files to be sharpened.

By referring to Figure 1, it will be seen that the tube 47 is provided with an insulated conductor Wire 59, the lower end of which is divided into two strands 60 which pass laterally through an opening 61 formed in the bakelite block 45 and are terminally connected to the above mentioned bolts 48. Also an insulated wire 62 is bared at spaced points 63 and secured at the bared points to the metal cylindrical base flange 19 ofthe tank, by means of bolts 64. A conductor wire 65 is also connected to one of these bolts and leads to any suitable source of electric current, such as a 110 volt alternating house current, as shown best in Figure 10.

As also shown in said figure, the wire 59, car ried by the tube 47, is connected to said sourc of current and preferably a rheostat 66 or transformer, if preferred, is interposed in the circuit with the wires 59 and 65 so that a low voltage. such as for instance two volts, may be maintained duringthe sharpening operation. The tank is insulated from its supporting cylindrical base, hereinafter described, as shown in Figure 1, so that the current passes from the rheostat through the wire 59, copper disks, files, electrolyte, damp wall of the earthen vessel, hot water, tank wall, and returns through the wire 65 to the rheostat. The direction of flow is the reverse from the above when the cycle reverses.

Forsupporting the vessel 23 in the water tank, a plurality of angular metal brackets 67 are secured to the inner wall of the tank above the heaters and project radially underneath the vessel. Upon these brackets there is mounted a grid 68, of the general shape shown in Figure 3. and which comprises an outer ring 69, an inner ring 70 concentric therewith and a center boss '71, these parts being connected by arcuate spokes 72, while certain other arcuate spokes 73 connect the outer ring with the inner ring and ter- This grid is preferably formed of copper and is insulated from the bracket 67 by means of a ring 74 of bakelite or other suitable material. The insulating ring is provided with a circumferential upstanding flange 74 which engages the outer ring 69 of thegrid andcenters the grid on the brackets 67.

The earthen vessel 23 is mounted direct upon the grid 68. It will thus be apparent that the skeleton structure of the grid permits of the water in the tank contacting with the bottom face of the vessel so that the temperature of the water will readily be imparted to the bottom of the vessel, while at the same time the metal grid provides easy paths for the low voltage current passing to and from the electrolyte through the damp bottom of the vessel in a general radial direction across the bottom of the vessel.

It will be apparent that since the earthen vessel is nested within the metal tank in contact with the hot water in the latter, the electric current will flow from the axis of the vessel radially through the heated electrolyte and through the files to all points of the wall of the tank. Consequently, when alternating, pulsating, or reversing current is used, the copper in the electrolyte will be deposited uniformly through the entire surface of each file and then carried off therefrom when the cycle reverses, to cause a uniform cut, or removal of a thin skinof the file throughout the entire superficial area thereof so that uniform sharpening of the cutting edges will be produced, and objectionable taper positively obviated. At the same time, due to the uniform flow of current, through the uniformly heated water bath in the. tank, spotting of the electrolyte will be eliminated and the objectionable pitting and deposits caused by spotting will consequently be positively obviated.

The above mentioned base for supporting the tank is designated by the numeral 75. It is preferablyformed of steel and is cylindrical in contour and is of sufficient diameter to permit of the tank loosely telescoping therein for a short distance, as shown in Figure 1. The base is insulated from the tank wall by a ring 76 of bakelite, or other suitable material. A plurality of angle brackets 94, similar to the vessel supporting brackets 67, are secured to the inner surface of the base. and extend radially underneath thegtank to support the weight of the tank andits contents. Aring 95 of bakelite or other suitable material is interposed between the brackets and the bottom of the tank to insulate the tank bottom from the base.

The base may also be provided with a hinged door 7'7 through which access to a gas heater 78, to be used for demonstration or for experimental purposes where electric current is not available. may be had. The burner is best shown in Figure 9, and. may be of the ordinary type equipped with an 'air valve'l9. The burner may be located directly underneath the bottom of the tank so as to discharge its flame upwardly against the bottom of the tank.

The base is also provided in its wall with an opening 80 through which a pipe 81, carried by the bottom of the tank, projects, as shown. The lateral arm 82 of the pipe is threaded into the T coupling 83 of the pipe so as to permit of said arm being removed so that the tank may be detached from the base when necessary. This pipe may be used as a steam pipe to heat the water in the tank, if desired, or may be used as a drain pipe, if desired, or even to fill the tank.

In some instances, it will be desirable to suspend the files. without removing their handles, as shown inFigure 8, in the electrolyte. For this purpose a holder is provided comprising a copper disk 84 having a plurality of radially disposed slots 85 and 86 extending from the outer edge toward the axis of the disk. The slots 85 are short and the slots 86 are relatively long and alternate. The files 87, equipped with their handles 88, may be inserted downward through the slots until the handles engage the disk and support the files on the disk but extending below the disk.

A tube 89 is threaded into the center of the disk and is equipped with a hook 90 for engagement with the bakelite link 91 of a suitable hoisting apparatus for raising the disk out of the electrolyte and for lowering it into the electrolyte. A circuit wire 92 is secured by a screw 93 to the metal tube 89, as above described.

Preferably the electrolyte comprises a mixture of copper sulphate, sulphuric acid, borax, and acetic acid.

From the above description it is thought that the construction and operation of my invention will be fully understood without further explanation.

What is claimed is:

1. Apparatus for sharpening files comprising a tank adapted to be filled with water, an electric heater immersed in the tank for heating the water, means for connecting the heater to a source of current supply, an earthen vessel nested within the tank in contact with the water and adapted to contain an electrolyte, a holder for supporting the files in the vessel in contact'with the electrolyte, and means for connecting the tank and the holder in circuit with said source of electricity. I

'2. Apparatus for sharpening files comprising a metal tank adapted to be filled with water, a metal base for the tank forming a compartment below the tank, said tank having a heat insulated wall, an electric heater immersed in the tank near the bottom, a casting in said wall of the tank removably supporting said heater, an earthen vessel nested within the tank adapted to be heated by contact with the waterand adapted to contain an electrolyte, a holder for supporting files in the vessel in contact with the electrolyte, means for connecting the tank and the holder in circuit with a source of electricity, and means for connecting said heater with said source of electricity.

3. Apparatus for sharpening files comprising a metal tank adapted to contain water, an electric heater immersed in the tank near the bottom thereof, a metal grid concentrically disposed in the tank and insulated from the inner surface of the tank, an earthen vessel supported in the tank on said grid and adapted to be filled with an electrolyte, a holder for supporting files in the electrolyte in upright position above said grid, means for connecting the tank and the holder in circuit with a source of electricity, and means for connecting said heater with said source of electricity.

4. Apparatus for sharpening files comprising a metal tank adapted to be filled with water, an electric heater carried by the wall of the tank and projecting axially to approximately the center of the tank for heating the water, brackets carried by the inner wall of the tank, an insulating ring carried by the brackets, a metal grid supported by said ring having curved radial spokes extending toward the axis of the tank, an earthen vessel in the tank supported upon said grid and adapted to be filled with an electrolyte, a holder for supporting files inrthevessel in contact with the electrolyte above thegrid, means for connecting the tank and holder in circuit with a source of alternating current, and means for connecting said heater with said source of current. i

5. Apparatus for sharpening files comprising a metal tank adapted to contain water, an earthen vessel supported axially in the tank in contact with the water and adapted to contain an electrolyte, an electric heater carried by the wall of the tank and immersed in the water below the bottom of the vessel, a file holder submerged in the electrolyte, means carried by the holder for supporting files in upright position in the electrolyte, circuit wires connecting said holder and said tank with a source of alternating current, a rheostat for varying the voltage of the current carried by said circuit wires, and circuit wires connecting the heater with said source of current.

6. Apparatus for sharpening files comprising a metal tank adapted to contain water, an earthen vessel supported axially on the tank and spaced above the bottom thereof and adapted to contain an electrolyte, an electric heater carried by the wall of the tank below the bottom of the vessel and above the bottom of the tank, a cover for the tank having a central opening loosely receiv-' ing the vessel and permitting escape of vapors from the tank, said cover sloping downwardly fromthe wall of the tank to said opening whereby water may be poured on to the cover to escape downwardly through said opening for replenishing the tank, a file holder removably disposed within the earthen. vessel in contact with the electrolyte, means for connecting said holder and said tank in circuit with a source of electricity, and means for connecting said heater with said source of electricity.

7. Apparatus for sharpening files comprising a metal tank adapted to contain water, an electrical heater, an earthen vessel adapted to be suspended axially in the tank and adapted to contain an electrolyte, a file holder removably disposed axially in the vessel and having a pair of spaced disks, provided with aligned openings to receive the shanks of the files and support the files upright in the electrolyte, legs on the lowermost disk for supporting the holder on the bottom of the vessel, means for connecting the holder and the tank in circuit with a source of electricity, and means for connecting the heater in circuit with said source of electricity.

8. Apparatus for sharpening files comprising a metal tank adapted to be filled with water, an electric heater immersed in the tank, an earthen vessel disposed axially in the tank and adapted to contain an electrolyte, a file' holder suspended in the vessel in contact with the electrolyte and having a slotted disk adapted to receive the files and engage the file handles to support the files in the electrolyte below the disk, means for connecting the tank and the holder in circuit with a source of electricity, and means for connecting the heater with said source of electricity.

AUGUST A. ROTH. [L.s.] 

